Posted
by
timothyon Saturday January 30, 2010 @03:27AM
from the sounds-like-a-fine-idea-to-me dept.

quaith writes "US astronomer Frank Drake has told scientists at a special SETI meeting in London that earthlings are making it less likely that we will be heard in space. In the past, we used huge ground stations to broadcast radio and television signals which could be picked up relatively easily — according to astronomers' calculations anyway. Now we use satellites that transmit at 75 watts and point toward Earth instead of into space. In addition, we've switched to digital which makes the transmissions even fainter. Drake has concluded that very soon, in space no one will hear us at all. I guess we'd better keep listening."

Correct me if I'm wrong (I very well may be; I'm not overly familiar with the Drake equation), but doesn't that broadcasting time apply mainly to before a civilization has the technology to broadcast? What about when they still broadcast, but in such a way that their signals don't pollute deep space? Is that taken into account?

Reading the wikipedia page further, it seems like his understanding of L is that it represented how long a technological society would be capable of broadcasting into space. So it seems like he didn't actually consider that as technology advanced civilizations would significantly reduce the amount of stray emissions. As a result his guess for L was around 10000, a few orders of magnitude off it would seem.

i would say we humans have actually increased our use of EM transmissions the last couple of decades. But said transmissions are shorter range then the EM thats been broadcasting since the start of the 1900's.

No. Civilizations that have moved far beyond radio for their own use will still understand that radio is an easily discovered, created, and maintained technology with great range and excellent economy. If such a civilization were to wish to keep track of emerging civilizations (a good idea, as the earlier it is done, the less dangerous they will be), they would keep radio reception going. Given our knowledge of physics, it seems that radio is as fast as anything can be - light speed - and so it would provi

Be sure to broadcast all the information that was included on the Voyager probes... you know, like our physiology and location... it's hard to plan a menu if you don't know what you will be using as the entree. Hey, we could end up as the secret ingredient on some sort of galactic "Iron Chief" program!

Digital wires interfere with each other via RF. There's no way to make a DSP chip complex enough to do digital voice or video without first having a very firm grasp of RF. Meaning "primitive" digital transmissions would be on-off keying at 100 baud or something like that. Which is as detectable from space as AM radio.

So even if we do happen to pick up radio signals from the 100 or so year window, during which aliens would be broadcasting radio waves, by the time we hear them, they could have been long extinct due to some catastrophe.

This is why the Drake equation never did seem to make much sense to me.

Given the rapid advancement of telecommunications technology we've observed, to me it seems entirely possible that a civilization a few hundred or thousand years beyond ours might not even be using a technology analogous to RF transmission. Entanglement, gravitation manipulation, something entirely different?

We can only imagine, because who can say what discoveries the future will hold, but you can be damn sure that a thousand years fro

Why do people keep suggesting entanglement as a future communication technology? It doesn't transmit any information. (And if you say "But what if it does and we don't know yet?" then you're not talking about entanglement, you're talking about some random undiscovered physics and using the wrong word for it.)

This is why the Drake equation is correct, but useless. Every factor in it is a guess that slides along a scale from "observational estimates" to "wild assed". And by careful selection of just the right guesses, you can come up with a number that suggests dumping truckloads of money into SETI is worth it. But any one of those numbers can skew N to less than one in a heartbeat.

And now, with just one the values that they based the decision to build SETI on reduced by three orders of magnitude, based on jus

Yes, but the assumption was that civilizations stopped broadcasting into space because they ceased to exist. Now we can think, maybe there are civilizations out there that are extant, but past the point of radio broadcasts. This is good news if we hope that intelligent life is still out there.

Right, but I am pretty sure the assumption was that this length of time is generally a lot longer than it actually has been for us... for the simple reason that ubiquitous low-power transmission was not foreseen as a partial replacement for centralized, high-power transmission.

So if a sufficiently advanced civilization (like ours) eventually develops radio technology that doesn't get far beyond their own planet, could this severely limit how much we would detect from other planets in the way of radio signals?

Imagine a sphere of radio transmissions expanding at the speed of light from every civilized planet - sooner or later these are going to permeate space, so if you can't detect anything it starts to look a bit odd.

Now imagine that civilizations typically switch to non-broadcast and/or digital signals (the latter, if efficiently compressed, will "sound" like random noise) within a century of inventing radio. Instead of spheres, space will be full of 100 light year thick "shells" of easily detectable signals. So its far more likely that we find ourselves in one of the gaps between shells.

Of course, the Drake equation/Fermi paradox ideas are only plausibility arguments, make all sorts of assumptions about how civilizations develop based on extrapolation from one data point (us).

It would be easier for us to inhabit the Moon or Mars or the oceans or underground or where ever than to go to a new solar system. I imagine that by the time a civilization has the power to go to another solar system for colonization issues of overcrowding would be overcome by technology. If they can get here they'll probably either come for research or just to fuck with us.

I imagine that by the time a civilization has the power to go to another solar system for colonization issues of overcrowding would be overcome by technology.

I'm sure the Native Americans that occupied North America would have thought that about the Europeans, too.

It is really hard to make any assumptions about why aliens might show up on our doorstep. There are logical explanations for why a peaceful, curious society would make the journey, but there are equally logical explanations for a hostile society. Certainly, the ability to develop long distance space travel means that a society has a high level of organization and cooperation. But we have seen that here on earth with both the United States and Nazi Germany. We also know that military conflict can be a great motivator to developing some kinds of technology, so visitors to earth might arrive in warships.

The bottom line is we just don't know and no explanation seems any more plausible than any others.

Interstellar space is even more inhospitable than the moon or Mars. If you've developed technology where you can live in tin can for extended periods of time and travel light years across the galaxy, then living on a place like the moon or Mars is relatively easy.

Once we develop such a technology the only need is to collect raw materials. There isn't really a need to settle on a planet because the spaceship would be a more hospitable place than any alien world.

Not if they have any economic sense in their heads. Unless the aliens have some sort of magic infinite energy source or teleportation device, the cost of transporting an invasion fleet to another solar system would be orders of magnitude higher than the value of anything they could possibly gain from Earth. And if they do have an infinite energy source or teleportation device, then they could use those inventions to provide for their needs directly, without leaving their home.

So if aliens invade, it will be for solely their own entertainment, not for economic reasons.

If you're an alien dude who wants to score with the alien chicks, you might just impress them by collecting humans. You could embed a human in a chunk of pure carbon-12 diamond, mount that in an iridium ring, and slip it onto her tentacle. She might have thousands of tentacles.

Maybe you collect humans to sell as an aphrodesiac. You puts the heads on top of a snack, kind of like sea urchin eggs on sushi.

Maybe you lay eggs in the humans. Ever see that movie with the pods? The aliens take over human bodies. An

Unless the aliens have some sort of magic infinite energy source or teleportation device, the cost of transporting an invasion fleet to another solar system would be orders of magnitude higher than the value of anything they could possibly gain from Earth.

Doesn't that assume minimal technological progress? It could be that the cost of transporting an invasion fleet great distances could be much less for a sufficiently advanced civilization. Technology has a way of becoming cheaper over time.

you haven't thought this out. energy isn't the only resource they might require (too much peak oil bunk you've been reading i suspect). a habitable planet is worth a lot more then just energy. even a huge energy source is useless if you don't have air to breath.

*: Pink Goo is mankind. It replicates relatively slowly, but some people think it will nevertheless fill any amount of space given enough time. In the pink goo worldview the spread of humanity is a catastrophe and space exploration opens up the possibility of the entire galaxy or the universe getting filled up with Pink Goo - the ultimate crime, something to be stopped at any cost.

The possibility of extra-terrestrials intercepting our signals, being
interested in them, replying before humanity has run its course, and
something good coming of it, are so remote that it's not worth
constantly wasting energy for the purpose. If you look at Earth from
space you realize what a tiny, limited, fragile place it is and how
important it is that we do all we can to make us "live long and
prosper". Hoping that aliens are going to help us in any way is
counter-productive.

The flip side, of course, is that monitoring for radio signals is extremely cheap. It uses equipment that we already use for other purposes and a small number of researchers. The potential upside is huge, though. Discovering that an advanced civilization exists somewhere is such a big deal that there is no reason not to do something cheap and easy to find it.

I agree that the odds are stacked against us and that it is unlikely that we find anything. Even if we are lucky enough to pick up a signal, establishing communications would be difficult. The odds are stacked against us, no question. But we are a curious species and we just can't pass up an opportunity to learn something, especially when it costs us so little.

And this is a possible answer to the Fermi paradox. Well, after you accept that interstellar travel is not economically feasible.

Broadcast is not a great communication strategy. On-demand point-to-point communication takes over most things. Advanced civilizations go silent from the outside within a blink of them transmitting their first broadcast signals. There's no reason to think that we'll ever put serious effort into sending signals into the black given all the other things on our plate. And there's no reason to think that any other civilization would have such extra resources either.

There's no reason to think that we'll ever put serious effort into sending signals into the black given all the other things on our plate. And there's no reason to think that any other civilization would have such extra resources either.

Sure there is... it's not like putting up a few beacons is hard to do, as evidenced by the fact that we were able to do it, unintentionally, even back in the 1920's.

Whether or not we (or any hypothetical aliens) would want to do it is another question, but certainly any tech

And this is a possible answer to the Fermi paradox. Well, after you accept that interstellar travel is not economically feasible.

Except no-one in their right mind would accept that. The cost of an interstellar colonisation flight would be small compared to the value of another solar system, and the cost of not expanding to other solar systems would be the death of our species.

Given that any alien race who chose to expand could colonise the entire galaxy in under ten million years without even trying hard (or a hundred million years without trying at all, just by tourists on a random walk), the answer to the Fermi Paradox is simple: there aren't any... if they existed, they'd be about as hard to spot as technological life in Manhattan.

Except no-one in their right mind would accept that. The cost of an interstellar colonisation flight would be small compared to the value of another solar system, and the cost of not expanding to other solar systems would be the death of our species.

The economic return of interstellar colonization is zero.

The only return is darwinistic. Not all our eggs in one biological basket, and all that. However, unless we're damn sure the target system has an earth-like breathable, survivable biosphere, then we may as well stick to this system. We're not exploiting most of it at all. We -might- find an oxygen atmosphere, heated water laden, near-1g planet "nearby" (100 ly) but it's unlikely. What's nearly impossible is finding one with a biosphere that we can survive in without basically obliterating it and dropping down earth biologicals. Most things on such a planet would poison us.

Unless such a magical planet is found, exploring outside our system before serious colonization (which -could- be economically valuable) of Mars, gas giant moons, etc is a waste. On all levels.

What's nearly impossible is finding one with a biosphere that we can survive in without basically obliterating it and dropping down earth biologicals. Most things on such a planet would poison us.

Most biological poisons are highly evolved and specialized. It's unlikely that any alien species would have developed poisons that target humans. Other than that, life throughout the universe probably uses mostly the same sugars, amino acids, and DNA. There may be some unusual compounds, but they would just be i

In the Western world, the economic return of having children is often considerably less than zero. Yet people keep doing it. I wonder why? Could it be that there are more things to consider than simple economics? I think that just might be possible.

Why do you think finding an Earth-like world within 100 light years is "unlikely"? We have already discovered worlds with liquid water. Unfortunately, so far they have been far too large for us... but that's just because the big ones are easier to find. In just the last year we have found several planets closer to earth's size.

Given our actual experience of the last couple of years, I don't think it's "unlikely" at all. I think it's quite likely indeed.

The cost of an interstellar colonisation flight would be small compared to the value of another solar system

Value to whom? Investors get no ROI.

and the cost of not expanding to other solar systems would be the death of our species.

Sufficiently advanced civilizations may not care. Remember that even at the individual level, many people choose not to procreate and don't fear death. An advanced civilization may realize that a good few million years on their own planet, maybe even without a lot of technology

I think it's a pretty ignorant statement to presuppose that any other civilization in the universe will necessarily irreparably rape and exploit their planet for resources as badly as we humans have.

I think it's a pretty safe bet. Nor is it necessarily as negative as you make it out to be. Europe "raped" its continent, radically altering the ecology, exterminating and introducing species, and mining natural resources to near depletion. Is Europe a barren desert now? Is it populated by impoverished nomad

Considering how the meeting between two civilizations, one more avanced than the other has generally gone badly for the majority of human history, it may not be such a bad idea to keep ourselves quiet until their intentions are shown to be peaceful/cooperative.

Violence doesn't matter, since it makes no difference whom initiates, so if the less advanced civilization is more violent the end result is the same as if the more advanced civilization is more violent.

Since we still pump large amounts of light into space from street-lighting around the world would that not be easier to detect than a few encoded radio signals?

Even if they detect a digital signal they still have to demodulate it to this obscure 'base-2' encoding we use over here because it works well with our equipment they have either grown out of or never discovered, after that they might decide to visit asciitable dot com [asciitable.com] to find out what it actually means.

This "light pollution" is completely negligible. First of all it is entirely negligible compared with the sunlight reflected from Earth. Secondly, the sun is orders of magnitude brighter. Seeing a small planet that close to the sun is nearly impossible. Adding 0.001% [number made up by me] to the planet's luminosity won't make a difference.

How many orders of magnitude more visible light do we emit than radio waves? In about 20 years we'll have the technology to directly image an extrasolar planet on a fairly consistent basis. Not long after that, we'll probably be able to detect artifical lights on the surface of an extrasolar planet on its night side. This is probably far easier than trying to fish out their extremely diluted, planet directed signals.

I think the signal-to-noise ratio matters more than the luminosity here. The signal due to "artifical lights on the surface of an extrasolar planet on its night side" will surely be swamped by simple fluctuations in the output of the star. IANAAstrophysicist but my guess is that the radio background from the sun is far weaker than the visible light background .

We have large synchronized power grids. They'll get a signal that's 2x the line frequency. As the Earth turns, you get modulation of various sorts: frequency, phase, amplitude.

Amplitude goes down for oceans, and up for land. You get more 100 Hz for the Old World, and more 120 Hz for the New World. As different country-sized areas with the same line frequency pass into view, you get phase change.

I was under the impression that historically, our radio and tv signals didn't even make it to Alpha Centauri. Unless we suddenly discover extra-terrestrial life inside of our solar system, does the switch to digital really change anything? Correct me if I am wrong, please.

Radio waves spread in accordance with the inverse square law. For every doubling in distance traveled, they become 1/4 as strong. It may well be that the *practical* limit for detecting our own tv/radio signals is somewhere near Alpha Centauri, but that's a limit imposed by our own equipment. The signal propogates forever, or at least until it's stopped by another planet/star/comet/dust/whatever. And space is mighty vast and mighty empty.

Do we WANT to be detected? Oh it would be wonderful if we could communicate with intelligent life somewhere other than earth (I am assuming there is intelligence here). But what if the species we contact are not peaceful? What if they're out looking for worlds to enslave? There certainly would be an advantage in staying quiet and being the first to "discover" a new civilization without giving up our own presence. That way we could study these new beings before deciding whether to risk contact or not.

Likewise, the same logic can be applied to an alien species. Why would they trust us? Why would they carelessly beam their presence out into space, not knowing who was going to listen in? It is certain, given our past history (you know, that part about strong humans usually ending up wiping out weaker ones through conquest), that we ourselves aren't exactly trust-worthy. Maybe they have heard us, and we failed the test, and we will never meet our neighbors. That is one possibility the "Drake Equation" fails to account for. Maybe we will be permanently assigned to the universe's "time out" box, because of our bad behavior - and we'll never know.

There's a lot the Drake Equation fails to account for. As a mathematical estimate, it's fairly useless. Its chief contribution to science (although some might question whether this is a contribution) is that it gets people talking about extraterrestrial life.

Has anyone considered the historical evidence of what happens when superior civilizations encounter lesser ones?
The Native Americans, the Mayans, the Incas, the Australian Aborigines, the tribes of South America, the natives of Pacific Islands, to name a few, all cry out to humanity to avoid at all costs encounters of the first, second, and third kinds.
We have no reason to expect anything but annihilation from advanced alien races-
either they are truculent and violent like we are, or they will destroy us as a service to the rest of the galaxy.
We do not wants aliens to find us!

Has anyone considered the historical evidence of what happens when superior civilizations encounter lesser ones?Has anyone considered the historical evidence of what happens when human civilizations who feel superior encounter ones they consider lesser?The Native Americans, the Mayans, the Incas, the Australian Aborigines, the tribes of South America, the natives of Pacific Islands, to name a few, all cry out to humanity to avoid at all costs encounters of the first, second, and third kinds.We are so ignora

Has anyone considered the historical evidence of what happens when superior civilizations encounter lesser ones? The Native Americans, the Mayans, the Incas, the Australian Aborigines, the tribes of South America, the natives of Pacific Islands, to name a few, all cry out to humanity to avoid at all costs encounters of the first, second, and third kinds. We have no reason to expect anything but annihilation from advanced alien races- either they are truculent and violent like we are, or they will destroy us as a service to the rest of the galaxy. We do not wants aliens to find us!

Not a problem, unless they're very long lived or really have found a faster than light travel mechanism. Civilizations that were conquered on earth were all reachable well inside a human lifetime. What's more the civilizations all had things of value to the invaders - land, resources, natives to indoctrinate in their religion. Any civilization sufficiently advanced to invade would likely be able to obtain their resources more locally, and colonise more local uninhabited worlds. I would hope they're past superstition, but who knows.

Has anyone considered the historical evidence of what happens when superior civilizations encounter lesser ones?

No, as it turns out, you're the first person ever to consider it. The first person in the entirety of human history. Even as I type, the Nobel Committee are holding an emergency session to create a new honour that's significant enough to even begin to recognise the enormity of your insight. Do not leave your home: a team of crack sculptors are en route to measure you up for your 400 foot tall solid gold statue.

Has anyone considered the historical evidence of what happens when superior civilizations encounter lesser ones?

That analogy doesn't work. Among other things, aliens can't mate with us and they're probably not going to carry pathogens that can infect us, and those two factors strongly influenced the outcome of European colonization.

(Like Europeans, aliens may be religious nuts bent on destroying our religion and replacing it with their own, but that seems somewhat unlikely.)

There have been several attempts [wikipedia.org] at sending radio messages into space specifically for communication purposes. Whether we keep that up or not is independent of our use of radio for intraplanentary communications.

Why are so worried about finding aliens right now? Its like a child trying to throw a paper plane to the top of a mountain. We need better technology and it will be here soon. Best not worry where we're pointing our signals at the moment.

The freespace loss from Earth to anywhere outside of the solar system is so incredible that fretting over a couple hundred dB out of literally trillions seems ridiculous, especially with the enormous noise source of the sun practically on top of us (in a galactic sense).

I've always thought the idea that an ET would detect our Radio/TV signals to be romantic at best. This is also why SETI is pretty much pointless.

Our communications signals are getting weaker, sure, but we still have other sources of clearly artificial radiation that are just as powerful as before. For example, military and weather radar. We regularly send out radar pusles powerful enough to compute the range to other planets in the solar system. Similarly, the Deep Space Network sends out powerful signals on various frequencies using highly directional beams when communicating with space probes.

To think that aliens will be using radio is like Geronimo thinking the people in Europe used smoke signals.Wish I could tell you what they are using, but as we haven't invented or noticed it yet, your guess is as good as mine.(For my guess I'll say they're using Quantum Filament Transmission Sequencers. Whatever that is.)

I don't begrudge the idea of searching for alien radio signals, we might luck out and find one and actually recognize it for what it is, but I'm not holding my breath.(Besides, foreign art

I've been critical of SETI efforts for this reason. Much SETI effort was focused on looking for "carriers", big constant-frequency RF sources. Broadcast AM, FM, and analog TV (which was AM video, FM audio) have strong carriers, but that was hugely inefficient. About 80% of an analog TV station's power output wasn't conveying any information other than "We're here". As receivers improved, new RF technologies used weaker carriers, then suppressed carriers, and finally, with spread spectrum, dropped the whole concept of carriers. Many modern RF signals appear to be noise unless you understand the encoding. (The same thing happened to modems decades ago; at 300 baud, you heard tones; at 9600 baud and up, it sounded like white noise.)

I once pointed out to a speaker at Stanford promoting some SETI scheme that they couldn't detect any emission that the FCC would now license for a new application. He admitted that was true. For our civilization, there was less than a century of high-powered carriers. That's a narrow window to hit for SETI purposes.

Arguably, though, any sufficiently advanced civilization will monitor all RF passing through their solar system and will be able to detect anything which has a pattern which can be synched up. Although carriers are going away, all signals between distant points need some form of synchronization information. The synch information may be a tiny fraction of the transmitted data, but there has to be something upon which the receiver can lock.

Haha actually that's a pretty good thought. Good encryption should yield a signal resembling one of maximum entropy... meaning that it would hardly be distinguishable from noise.

On the other hand, if it were not the data itself but the character of the signal that were detectable, that's another story altogether. For example, the equivalent of TCP/IP packets would be easily detectable as intelligent signals, regardless of the eventual content of those packets.

In another galaxy, a frustrated physics professor is in charge in a project equivalent to SETI:

"Stultz, I wonder if there is actually life out there. We've been centuries monitoring the neno-kurflichsk time-fabric disturbance detector that any technologically advanced civilization should be sending out if...if... they sentients do exist. I mean, it is third grade stuff, anybody knows that time-fabric can be disturbed instantly, we keep doing it simultaneously to all the atoms of the universe, and still nothing for CENTURIES. Can you believe it?"
"Professor, I wonder... I have this crazy idea... maybe other other advanced civilizations use... radiowaves?"
"Stultz, you are an idiot or what?"
"I...I am just saying, maybe some less advanced civilizations..."
"Pluuhlease, that is enough! Are you serious? You should go back to elementary school. Have you forgot that radiowaves travel at the speed of light??, it is more than obvious that it is not the most convenient way to communicate with other civilizations... unless you want to wait another lifetime to send your response, and to where should we point the antennas, huh?. Have you forgot that we are talking about ASTRONOMICAL DISTANCES??
It would take centuries! Or even worse, those electromagnetic waves would be absorbed by black holes, bounced, even hit by the breshanistok matter! We would get nothing or everything scrambled, indistinguishable from white noise! Your question is simply retarded. We are trying to contact sentients, not idiots!"

And professor Breshanistok stood up upset and the graduate student Stultz watched the glowing monitoring holoscreen scratching his head.